NEW ORLEANS – according to an interim analysis of a postapproval clinical trial.
Testosterone nasal gel is a shorter-acting formulation of testosterone that “can mimic normal physiology,” said John Masterson, MD, a urology resident at the University of Miami. The 4.5% formulation, which was approved by the Food and Drug Administration in 2014 and is marketed as Natesto, delivers 11 mg of testosterone per dose and is dosed three times daily for testosterone replacement therapy.
The negative feedback exerted by other exogenous testosterone formulations on the hypothalamic-pituitary-gonadal (HPG) axis is known to inhibit spermatogenesis, Dr. Masterson said in a video interview at the annual meeting of the Endocrine Society.
Dr. Masterson, senior author Ranjith Ramasamy, MD, and their colleagues hypothesized that the shorter duration of action of testosterone in the nasal gel formulation would result in some conservation of gonadotropin-releasing hormone (GnRH) pulsatility, less inhibition of the HPG axis, and preservation of spermatogenesis.
In the same interview, Dr. Ramasamy, director of reproductive urology at the University of Miami, noted that “the levels of testosterone in men rise about an hour or 2 after administration [of the gel] and seem to drop off about 2 to 4 hours after the peak.” That is closer to normal physiology than other delivery systems in which “the levels of testosterone are pretty high during the day and therefore could lead to some of the side effects that we see with testosterone.”
The phase 4 prospective study enrolled 56 men aged between 18 and 55 years who had low levels of testosterone (baseline mean, 233.97 ng/dL). The mean age was 37 years.
“There are mostly younger men in our study ... and they’re usually coming in with one or two hypogonadal complaints – lack of energy, fatigue, some with erectile dysfunction,” Dr. Masterson explained in the interview. Improvement was seen in those realms, but the differences didn’t reach statistical significance, because baseline quality of life was already fairly high for these otherwise healthy men. “What we can say is that on the drug, quality of life certainly did not get worse,” he said.
At baseline, the mean luteinizing hormone (LH) level was 3.66 IU/mL, and the mean follicle stimulating hormone (FSH) level was 4.01 IU/mL.